Pesticide Residue Methods

QuEChERS: A Mini-Multiresidue Method for the Analysis of Pesticide Residues in Low-Fat Products

Method Date

2003/01/01

Method Type

Screening, Quantitative

Scope and Application

A Multi Pesticide Residue Method for the analysis of a side range of pesticides in low oil / fat crop matrices.

Method Summary

The homogeneous and representative subsample is extracted in frozen condition with the help of acetonitrile. After addition of magnesium sulfate, sodium chloride and buffering citrate salts, pH 5 to 5.5, the mixture is shaken intensively and centrifuged
for phase separation. An aliquot of the organic phase is cleaned up by dispersive SPE employing bulk sorbents e.g. PSA, GCB as well as MgSO4 for the removal of residual water. PSA treated extracts are acidified by adding a small amount of formic acid, to improve
the storage stability of certain base-sensitive pesticides. The final extract can be directly employed for GC and LC based determinative analysis. Quantification is performed using an internal standard, which is added to the extract after the initial addition
of acetonitrile. Samples with a low water content (LT 80 pct) require the addition of water before the initial extraction to get a total of ca. 10 mL water. When dealing with samples containing LT 25 pct water e.g. cereals, dried fruit, honey, spices the size
of the analytical sample may have to be reduced e.g. 1 to 5 g depending on the load of matrix co extractives expected in the final extracts.